Maybe Ultrasone have been selling better so now they get sales.
Sellers just finally putting them on sale. Distribution and sellers working together to make the Ultrasone cheaper but sell better.
Whatever it is they are indeed a lot cheaper than they were.
Just open air models haven't been put on sale Pro 2900 and HFI 2400.
Ultrasone are headphones that offers the most unique sound so really the only ones really worth giving a shot if you want to really try something different to what you have already.
What I like about Ultrasone is -4db of air pressure other headphones drill sound into your ears.
Ultrasone tries to be like speakers and bring it more naturally and pleasantly.
The S-Logic is the driver being decentralized and letting the outer anatomy of your ear the pinna aka auricle each unique persons ear to collect that sound and then give it to you.
It also better a lot better and not being so left/right like other headphones can be still not quite speakers though.
Besides the air pressure everything is more pleasant and easier to listen to.
Drums and cymbals actually sound good.You can actually hear the bass other headphones wash over.
To me it's like speakers it's very easy to listen to and focus on what you want to.
After Ultrasone for me other headphones are way too tiring and fatiguing to listen to.
And even great recordings I find can be annoying with regular headphones the Ultrasone really is a brilliant design soundwise enjoyment wise not as good as speakers but the best headphones to me.
My experience is with open air models HFI 2200 which has been turned into HFI 2400 and Pro 2500 (out of production)
I haven't really got to try out a closed back model just one for a little bit not long enough to say anything.
Ultrasones also need to burn in no getting use to the sound they really change in sound from out of the box.
Also portables don't do Ultrasone justice at all..Maybe the HFI 580 can but I haven't tried that one.
Another thing compared to other headphones you might be shocked at the softer sound at first due to not having all that air pressure
you might need a little ear reset/brain reset. You might not like it at first it's like the loudness wars.
Ultrasone being dynamic and other headphones being brickwalled. Give it a good listen before judgement.
If your willing to I say give them a try.
As for which model can't say.
The Pro 900 is the only Ultrasone model on here that's been getting attention.
Looking at charts the Pro 900 really seems a lot brighter than all other Ultrasone models.